Latch designs need to accommodate different packaging requirements for lift gates, decklids and sliding doors. In addition, automotive companies are looking to provide new features for their vehicles, even on components such as latches. Features such as power locking, power releasing and power cinching are rapidly becoming popular. Other manufacturers desire simpler and less expensive locks. The need for multiple latch packages and feature sets results in the need for multiple latch designs while manufacturers are looking to standardize parts in order to reduce assembly costs. Therefore, it may be desirable to produce a modular latch that can accommodate different features within one assembly.
Additionally, in a vehicle collision, there is the potential that sudden deceleration may generate an inertial load on either the ratchet or pawl to accidentally release the latch. This may not be desirable.
For latches with power cinching, the controller needs to know the position of the ratchet (released, primary engaged, secondary engaged position), in order to know when to begin and when to stop the cinching motor. Typically, switches triggered by either the ratchet or the pawl, or both, tend to report on the ratchet position. FIG. 1a shows a prior art switching strategy. One switch is triggered by the ratchet, and another switch is triggered by the pawl. The ratchet switch has an OFF state when the ratchet is rotated into the release position, and an ON state when the ratchet is rotates past the secondary and preferably close to the primary engagement positions. To compensate for operational variances, there is a slight lag between the ratchet reaching the primary engagement position and the ratchet switch indicating that the ratchet is engaged. The pawl switch has a OFF position that corresponds to the pawl being actuated away from the ratchet, and an ON position, which corresponds to when the pawl retains the ratchet in either the secondary or primary engagement positions. One problem with this switch strategy is that the switches report the same state (OFF and OFF) when the ratchet is in the primary engagement position, and an interlude between the primary and secondary engagement positions. The controller is forced to use additional intelligence to provide the desired cinching effect, resulting in increased complexity and more expensive components.
A second prior art switch strategy, shown in FIG. 1b, uses two switches, but with both switches contacting the ratchet at different parts of the ratchet's travel between released, secondary engagement and primary engagement positions. The first ratchet switch works as the ratchet switch described above. The second ratchet switch is positioned elsewhere along the ratchet's travel path so that it is off when the ratchet is released, switches ON while the ratchet travels from secondary to primary engagement positions, and then switches off again. As before, operational variances require that there be a lag between the transition of the switch state and the ratchet position. While this switch strategy avoids the OFF, OFF scenario described above, the second ratchet switch is not turned off until after the ratchet reaches the primary engagement position. This results in the motor continuing to cinch briefly, but disquietingly, after the latch is fully closed in the primary engagement position.
Finally, it is generally desirable to reduce the cost of producing the latch. This includes reducing the product design and development costs, design validation and production validation test costs by using previously designed and validated components. This may reduce the number of components used during assembly, the time required to assemble the latch, and the cost of the components generally.